All the world’s plants are in here (well, almost…)

Plants of the World: An Illustrated Encyclopedia of Vascular Plants by Maarten JM Christenhusz, Michael F Fay and Mark W Chase, 2017. Kew Publishing/University of Chicago Press.

One of the great botanical pleasures I have had for many years is the joy of flicking through the pages of Vernon Heywood et al’s Flowering Plant Families of the World, both the original 1978 edition and 2007’s 2^nd edition. It was (and still is) a magical experience to open the book at random and read about a plant family. Oftentimes – to start with anyway (and increasingly these days as one forgets stuff…) – they were families I never knew existed, maybe having just a handful, or, occasionally, just a single, species in them. But all had a story to tell. And those stories were the ever-important reminders of both the botanical beauty that exists on this planet, and its bounty – typified in that ancient and fundamental bond that exists between people and plants in our use of, and dependence upon, plants and plant products. However, with Plants of the World by Maarten Christenhusz et al. [hereafter referred to as Plants of the World], we have a new kid on the block that challenges the position currently held by Heywood et al.

And what an impressive tome Plants of the World is!

Weighing-in at a coffee-table-busting 7 lb 2 oz., this 28.5 x 23.5 x 5.0 cm of hard-backed book begins – usefully, and importantly – with a 2-page spread entitled “How to use this book”. This guides the reader through the layout of a typical family entry, amongst which are the following sections: the family name and common name [all 451 families included have common names]; a map of the family’s approximate native range [remember, nowadays many of the plants are grown far beyond the places where they evolved]; a description of the family’s key botanical characteristics [for which an extensive Glossary is provided…]; a list of genera in that family (and the number of species therein in brackets); notes on uses of the species [though not for all families – however, if no uses are known, a statement to that effect would be useful, for consistency of family coverage, and to remove reader’s doubts], the origin of the family name, and comments on phylogeny and evolution [a discussion of our current understanding of the family’s place in the grand scheme of plant evolution]. The book’s default layout throughout is 3-columned text per page, except for the General Index, and the plant family indices on the inside front and back covers.

Plants of the World follows – much more rather than less (p. 10) – the most recent classification of the Angiosperm Phylogeny Group (APG) version IV (Angiosperm Phylogeny Group, Botanical Journal of the Linnean Society 181: 1–20, 2016; doi: 10.1111/boj.12385) re flowering plant families, the molecular classification of Christenhusz and Chase (Annals of Botany 113: 571–594, 2014; https://doi.org/10.1093/aob/mct299) for lycopods and ferns, and the conifer phylogeny of Christenhusz et al. (Phytotaxa 19: 55–70, 2011; doi: 10.11646/phytotaxa.19.1.3). Taxonomically, Plants of the World is therefore probably as up-to-date as such a book can be (and a major reason why it will differ from Heywood et al’s Flowering Plant Families of the World).

451 plant families covered

After short sections at the beginning of the book looking at such aspects as land plant evolution, plants and human culture, naming of plants, plant classification and phylogeny, fossil plants, etymology and common names, and economic botany, the encyclopaedia proper starts on p. 18 with the Lycopods (3 families, including number 1, the Lycopodiaceae (clubmoss family)). It goes on to cover Ferns (49 pp.; families 4 – 24), and Gymnosperms (16 pp.; families 25 – 36). Angiosperms – as befits their numerical superiority [c. 287,899 species of an approx. total of 300,750 vascular plant spp. recognised by the authors*] – occupy the bulk of the book (c. 550 pp.). This flowering plant section begins with the so-called ANA Grade families (7 pp., families 37 – 43 such as Amborellaceae and Nymphaeaceae), then Magnoliids (20 pp.; families 38 – 62), Monocots (98 pp.; families 63 – 140), and concludes with the Eudicots (425 pp.; families 141 (the Eupteleaceae (the Asian-elm family) – 451 (the Apiaceae (carrot family))).

There follow a most substantial, and illustrated, 33 pages of Glossary; 80 pages of Further Reading (in family number listing); and 21 pp. of General References. This mighty tome concludes with an extensive, 37 pp. of 6-columned (!!) Index of taxa, common names, and useful plants and products. Nominally, 792 pages long, it manages to squeeze in even more text on the inside front and back surfaces with 5-columned indexes, to plant families, and common names of families, respectively. Plants of the World is therefore a most impressive work of scholarship on many levels.

So far so good, but how does Plants of the World compare to Flowering Plant Families of the World?

In respect of much of the plant family information presented – structure, distribution, and economic uses – Plants of the World covers territory similar to that in Heywood et al’s Flowering Plant Families of the World. Classification is covered by both, but Plants of the World is the more recent and up-to-date. Plants of the World includes an important evolutionary dimension in terms of information about the geological age of the Orders (taxonomic units that include one or more evolutionarily-related families). And Plants of the World extends its coverage beyond just the Angiosperms of Flowering Plant Families of the World to all vascular plant families, i.e. to include lycopods, ferns and gymnosperms as well.

A particular strength of Plants of the World is the hundreds of full-colour illustrations – almost exclusively photographs (2500 according to the blurb on the book’s back cover…) – of the plants. Although individual images are sometimes a little on the small side, they are sufficient to recognise the plants and therefore fit for the required purpose. Plants of the World is a fantastic photofest of phytological facts. Although these full-colour photos contrast markedly with the coloured illustrations of Heywood et al., I have to admit to a fondness for the latter’s ‘drawings’ (and which are bigger than the images in Plants of the World).

Plants of the World is not a book you sit down with and ‘consume’ in one sitting. Rather, its numerous family entries are like the world’s most extensive and never-ending buffet, the contents of which intoxicating botanical banquet one samples at one’s leisure as the occasion – or need – arises. And given its up-to-dateness, and evident scientific rigour and erudition (c. 80 pages of Further Reading!!!), this is a never-ending feast one can return to time and again, and each time discover more new information.

So, Plants of the World clearly compares – very favourably – with Heywood et al’s Flowering Plant Families of the World. But, given that fact that the latter was published a decade ago, maybe one way to think of Plants of the World is as an illustrated, flowing narrative version of Mabberley’s Plant-Book: A Portable Dictionary of Plants, their Classification and Uses (4^th edition) [https://botany.one/2017/08/mabberleys-plant-book-book-plants/] [although without inclusion of mosses and important seaweeds of the latter tome…].

But, isn’t it all on-line?

One could argue that the information in Plants of the World is available on-line – and for free – in such repositories and data bases as Kew’s Plants of the World Online (POWO) [https://www.kew.org/science/who-we-are-and-what-we-do/strategic-outputs-2020/plants-of-the-world-online; http://www.plantsoftheworldonline.org/], World Flora Online [http://sweetgum.nybg.org/science/world-flora/], the conifer database [http://herbaria.plants.ox.ac.uk/bol/conifers], Global tree Search – “The most comprehensive database of tree species” [http://www.bgci.org/global_tree_search.php], and Carmen Ulloa et al’s Checklist of the Vascular Plants of the Americas [http://tropicos.org/Project/VPA] (Science 358: 1614–1617, 2017; doi: 10.1126/science.aao0398). And that’s probably true (or will be when the various projects are completed, e.g. in/by 2020 for World Flora Online). But, as much as we have these on-line sources, there is no substitute for being able to pick up a book and flick through the pages to revel at the vegetable wonders and facts within. And the vegetable wonder reviewed here is a true book-browser’s delight. Arguably, to use the ecological language of plant grazers and browsers, Christenhusz et al‘s Plants of the World is the ultimate herbivore’s guide to plant diversity.

In summary,

Christenhusz et al‘s Plants of the World is not only a very worthy successor to Heywood et al’s Flowering Plant Families of the World, it takes this visually-appealing, encyclopaedic cataloguing of plant diversity to the next level. Get hold of a copy and immerse yourself in the botanical riches within – as we all await the next generation text (that will include all the families of all the groups within the Kingdom Plantae…).

* Interestingly, this is a little out of line with estimates of 295,383 flowering plants out of a total of c. 308,312 vascular plants (Christenhusz and Byng, Phytotaxa 261: 201–217, 2016; doi: http://dx.doi.org/10.11646/phytotaxa.261.3.1) (although thereby proving the article’s contention that numbers of plant spp. increase year-on-year). But that’s the nature of estimates, and those figures differ from the 369,434 spp. of angiosperms, and 383,671 vascular plants, estimated by Eimear Nic Lughada et al. (Phytotaxa 272: 82–88, 2016; doi: http://dx.doi.org/10.11646/phytotaxa.272.1.5)…